The present invention relates in general to cutting drums of mineral mining machines and more particularly to apparatus for use with such drums.
It is known to mount the rotatable cutting drums of mineral winning machines on pivotable arms which can be raised or lowered in relation to the bodies of the machines to bring the drums into different working positions. It is also known to employ a cowl or blade, possibly of arcuate shape, which is positioned adjacent the periphery of such a cutting drum to assist in loading the mineral detached from a mineral face by the drum. With such an arrangement it is however necessary to re-position the blade depending on the direction of movement of the machine. Normally the blade is mounted on a support ring or the like which can be moved around the axis of rotation of the drum to re-position the blade. It is known from German patent specification No. 2 652 614 to provide apparatus in the form of double-acting hydraulic piston and cylinder units in the blade support ring which can be actuated to press a friction ring against the drum. In this way the blade and its support can be selectively coupled to the drum through the friction ring to move the blade about the axis of rotation of the drum as the latter rotates to re-position the blade. In order to release the friction ring coupling to free the blade from the drum, it is necessary to charge the units with pressure fluid in the opposite direction. The prior art arrangement also describes means for locking the blade in its desired position with the aid of a hydraulic friction brake which permits the blade to swivel should excessive loading force be encountered. The prior art apparatus is complex and relatively costly to construct and moreover should a fault occur in the hydraulic fluid supply the apparatus will be unusable. A general object of the present invention is to provide an improved form of apparatus of the known type for selectively coupling the blade to the drum.